The present invention relates to an improved process for the preparation of phenyl ketones. More particularly it relates to the said process for preparation of phenyl ketones having formula (I) by reacting biphenyl with the corresponding acylating agent over a solid acid catalyst. 
Where in R=xe2x80x94COCH3 or xe2x80x94COCH2CH3 or xe2x80x94COC6H5.
Ketones are used mainly as a photo initiator for special printing plates, as well as for organic synthesis. Phenyl acetophenone and phenyl benzophenone are mainly used as pharmaceutical (antifungal) intermediate [Zhongguo Yiyao Gongye Zazhi, 23(3), 100-1 (Chinese) 1992.]; [Walczak, Antoni; Rzasa, Jozef; Labus, Stefan (PrzedsiebiorstwoFarmaceutyczne xe2x80x9cjelfaxe2x80x9d Sa, Pol.). Pol. PL 170632 B1 Jan. 31, 1997, 3pp. (Poland)].
In the prior art, an acyl group is introduced in the aromatic nucleus by an acylating agent such as an acyl halide, or itself in the presence of homogenous catalyst such as AlCl3 or BF3 (Encyclopedia of chemical Technology, Vol-II, page 1055, 1944)
Other process includes Friedel crafts acylation of various aromatics with a wide variety of acylating agents and metal halides such as AlBr3, FeCl3, FeBr3, SbCl5, SbBr3, TiCl4, CbCl5, NbCl5, GaCl3 and ZrCl4. Some of these may give yields comparable to those obtained with AlCl3 (Friedel Crafts and Related reaction, Vol-111, Part-1, page-62, 1964, Ed. G. A. Olah).
Ortho- and para-acylated products of biphenyl have been made from the direct reaction of biphenyl with acylating agent or by the Fries rearrangement of aryl esters using Lewis acid catalyst, AlCl3 (Ullmanns Encyclopedia Vol. A-1, p. 209); Calvert, Carys (Contract Chem. Ltd., Prescot/Merseyside L34 9HY, UK). Symp. Pap.xe2x80x94Inst. Chem. Eng., North West. Branch, 3 (3, Integr. Pollut. Control Clean Technol.), 4.1-4.16 (English) 1992.
In one method propionylation of biphenyl with propionyl choloride was carried out using ZnCl2 which consist of 12% yield of 4-Phenylpiophenone (4-PPP) (Friedel carft Related reaction Vol-III, part-1, 1964, Ed G. A. Olah).
A method comparising reacting biphenyl with propionyl chloride in the presence of AlCl3 gives 65% yield of 4-PPP (Friedel carfts Related reaction Vol-III, part-1, 1964, Ed G. A. Olah)
Other process includes the preparation of 4-phenylbenzophenones (4-PBP) 74% by the benzolylation of biphenyl with AlCl3 using CHCl3 at room temperature. [Zhongguo Yiyao Gongye Zazhi, 23(3), 100-1 (Chinese) 1992.]; [Walczak, Antoni; Rzasa, Jozef; Labus, Stefan (PrzedsiebiorstwoFarmaceutyczne xe2x80x9cjelfaxe2x80x9d Sa, Pol.). Pol. PL 170632 B1 31 Jan. 31, 1997, 3 pp. (Poland)].
There have been known a number of methods for preparing phenyl ketones by reacting biphenyl with acetyl chloride, propionylchloride and benzoyl chloride respectively using Lewis acid catalysts. However the above methods are disadvantageous from the industrial point of view, because of low selectivity for 4-phenyl acetophenone, 4-phenyl propiophenone and 4-phenyl benzophenone and the catalyst used are homogeneous. Thus the large amount of base is required to neutralise the homogeneous catalysts.
The chemical industries are facing increasing pressure to reduce its impact on environment. This is particularly true in the production of phenyl ketones. Such reactions often require large quantities of minerals or Lewis acid catalysts which are destroyed or diluted during the aqueous work-up procedures, leadings to problems with equipment corrosion and expensive to treat. Furthermore, the reactions frequently use excess of reagents and are notoriously unselective. The overall result is excessive energy consumption, wastage of large quantities of Lewis acid catalysts and excessive impact on the environment. An additional major handicap of the homogeneous Lewis acid catalysts is the difficulty of their disposal, after use in the acetylation, propionylation and benzoylation reactions of biphenyl in an environmentally acceptable manner.
1. In view of the above mentioned drawbacks of homogeneous catalysts in the prior art process, it was found desirable during the course of the research work leading to the present invention to develop an environmentally acceptable solid selective, regenerable and recyclable zeolite catalysts for the production of biphenyl ketones and particularly 4-phenyl acetophenone, 4-phenyl propiophenone and 4-phenyl benzophenone in high selectivity from the acylation (acetylation, propionylation and benzoylation) of biphenyl with acetyl chloride, propionyl chloride and benzoyl chloride respectively, in the presence of solid acid catalyst composite materials alumino-silicate zeolite catalyst.
2. The AlCl3 catalyst cannot be used with a number of hetrocyclic system which are decomposed by it due to its higher Lewis acid strength.
3. The use of AlCl3 may give rise to some side reaction of intra-or intermolecular migration of alkyl groups, acylation and replacement of halogen atoms.
4. Difficult operational problem of corrosion.
5. Difficulty in the catalyst AlCl3 or HCl removal from the products.
6. Use of stoichiometric amount of catalyst in all the methods described above. Some of them are hazardous and difficult to handle. In some cases catalyst is consumed during the reaction and in some cases catalyst are less selective.
It is therefore an object of the present invention to provide an improved process for the production of phenyl ketones by the acylation (acetylation, propionylation and benzoylation) of biphenyl in the presence of zeolite catalyst.
Another object of the present invention is to obviate the drawbacks and limitations of the prior art such as removal of HCl from the product form during the reaction, use of AlCl3 give rise to many side chain reaction.
Still another object of the present invention is to provide an improved process which makes use of non-hazardous solid zeolite catalyst.
A further object of the present invention is to provide an improved process which leads to high yields of ketones and selectivity to para products resulting from high conversion of biphenyl and to provide an improved process which is safe not being prone to explosion.
The objects of the present invention are achieved by using microporous aluminosilicate zeolites as catalyst. In accordance with the process of the present invention biphenyl can be converted to 2-phenylacetophenone, 4-phenylacetophenone, 2-phenylpropiophenone, 4-phenylpropiophenone, 2-phenylbenzophenone and 4-phenylbenzophenone in the presence of a zeolite catalyst composite material aluminosilicate using solution of an acylating agent and biphenyl with stirring in an oil bath, such zeolites may be containing usually sodium or potassium but may further include other cations such as rare earth metals. The cations may be of the same type or of two or more different types.
Accordingly, the present invention provides a process for the preparation of phenyl ketones of formula-I, 
Wherein R represents xe2x80x94COCH3, xe2x80x94COC2H5 or xe2x80x94COC6H5, which comprises acylating the biphenyl with an acylating agent in an organic solvent in the presence of a solid crystalline microporous catalyst composite material wherein the molar ratio of biphenyl to acylating agent is 1:1 at a temperature in the range of 50-200xc2x0 C. for a period of about 20 hrs. and separating the desired product by conventional methods like gas-chromatography to obtain the desired product.
In one of the embodiment of the present invention, the acylating agent used is selected from the chlorides of acetic, propionic or benzoic acids.
In yet another embodiment of this invention the zeolite catalyst used in the reaction is selected from H-beta, H-Y, H-Mordenite, H-ZSM-5, RE-Y having molar composition in anhydrous state
M/n:AlO2:zSiO2 
(where M is proton or alkali or rare earth metals with valency n, and z is between 2-500) having SiO2/Al2O3 molar ratio of from 2-50 having a pore size of 5-10 Axc2x0.
In still another embodiment the organic solvent used is nitrobenzene.
The process of the present invention is that, it does not pose any risk of explosion.
Thus, the process of the present invention is effectively and efficiently acylate the para-position of the substrate while suppressing the acylation at the ortho and meta position.
The present invention is described in a further detail with reference to the following examples, which should not be, however constructed to limit the present invention in any manner whatsoever.